The protective shell can be only the bottom side which replaces the bottom of the case. The internal laptop batteries are quite safe to handle if you don't use anything sharp on them. We let people handle phone batteries for ages and they weren't nearly as protected as those old laptop battery tubes.

They were certainly more protected than the almost naked ones I see right now which I can singlehandedly bend (but won't given the fire hazard). And not LiPol batteries too, which are super nasty in that regard: the more energy-dense the battery is, the more of a hazard.

The phone batteries that people handled did store a lot less energy though.

Non-removable just means it's soldered down. Open a phone and you will see that the batteries certainly have just the kind of plastic shell that they always had.

most phones and tablets i've worked on recently certainly do not have any plastic shell on non-removable batteries; unless you consider shrink tubing a shell.

They are usually constructed of layers of battery material, wrapped in kapton tape or an equivalent, with the entire package shrink-tubed and a pigtail coming out the side for the device interface.

One could easily crush the unit by hand, the construction offers little to no protection from physical forces.